"There were five tall figures: two standing on the lip of the dell, three advancing. In their white faces burned keen and merciless eyes; under their mantles were long grey robes; upon their grey hairs were helms of silver; in their haggard hands were swords of steel."

"Men proved easier to ensnare. Those who used the Nine Rings became mighty in their day, kings, sorcerers, and warriors of old. They obtained glory and great wealth, yet it turned to their undoing. They had, as it seemed, unending life, yet life became unendurable to them. They could walk, if they would, unseen by all eyes in this world beneath the sun, and they could see things in worlds invisible to mortal men; but too often they beheld only the phantoms and delusions of Sauron. And one by one, sooner or later, according to their native strength and to the good or evil of their wills in the beginning, they fell under the thraldom of the ring that they bore and under the domination of the One, which was Sauron's. And they became for ever invisible save to him that wore the Ruling Ring, and they entered into the realm of shadows. The Nazgûl were they, the Ringwraiths, the Enemy's most terrible servants; darkness went with them, and they cried with the voices of death."

The Silmarillion, Of the Rings of Power and the Third Age

Very little is known of specific wraiths, except their chief, the Witch-king of Angmar, Lord of the Nazgûl.

The Ringwraiths were considered the most powerful of Sauron's servants:

"At length he resolved that no others would serve him in this case but his mightiest servants, the Ringwraiths, who had no will but his own, being each utterly subservient to the ring that had enslaved him, which Sauron held.

"Now few could understand even one of these fell creatures, and (as Sauron deemed) none could withstand them when gathered together under their terrible captain, the Lord of Morgul. Yet this weakness they had for Sauron's present purpose: so great was the terror that went with them (even invisible and unclad) that their coming forth might soon be perceived and their mission be guessed by the Wise."

Unfinished Tales, Part 3, Ch 4, The Hunt for the Ring: Of the Journey of the Black Riders

"Of Khamûl it is said here that he was the most ready of all the Nazgûl, after the Black Captain himself, to perceive the presence of the ring, but also the one whose power was most confused and diminished by the daylight."

Unfinished Tales, Part 3, Ch 4, The Hunt for the Ring Notes 1

"All except the Witch-king were apt to stray when alone by daylight; and all, again save the Witch-king, feared water, and were unwilling, except in dire need, to enter it or to cross streams unless dryshod by a bridge. Moreover their chief weapon was terror. This was actually greater when they were unclad and invisible; and it was greater also when they were gathered together."

Unfinished Tales, Part 3, Ch 4, The Hunt for the Ring: Other Versions of the Story

Second Age1500 The Elven-smiths begin the forging of the Rings of Power1600 Sauron forges the One Ring in Orodruin22511 About this time the Nazgûl or Ringwraiths, slaves of the Nine Rings, first appear3441Sauron overthrown by Elendil and Gil-galad, who perish. Isildur takes the One Ring. Sauron passes away and the Ringwraiths go into the shadows. The Second Age ends.

Third Age1100 The Wise (the Istari and the chief Eldar) discover that an evil power has made a
stronghold at Dol Guldur. It is thought to be one of the Nazgûl.1300 The Nazgûl reappear. The chief of these comes north to Angmar.1409 The Witch-king of Angmar invades Arnor. He is eventually defeated in 1975, but the North Kingdom had fallen.1980 The Witch-king comes to Mordor and there gathers the Nazgûl.2000 The Nazgûl issue from Mordor and besiege Minas Ithil.2002 Fall of Minas Ithil, afterwards known as Minas Morgul.2063Gandalf goes to Dol Guldur. Sauron retreats and hides in the east. The Watchful Peace begins. The Nazgûl remain quiet in Minas Morgul.

3018June 20 A host from Modor attacks Osgiliath, the Witch-king spreads fear and terror among the defenders.July 1 The seven Nazgûl from Minas Morgul, unclad and unmounted, cross the Anduin. From here they pass through Anórien, over the Entwade, into the Wold, and to the west-shores of the Anduin.July 17 The Nazgûl from Minas Morgul receive horses and raiment on the west shore of the Anduin above Sarn Gebir.July 22 The Nazgûl from Minas Morgul meet up with the two Nazgûl from Dol Guldur at the Field of Celebrant. Khamûl the Easterling reports that there are no dwellings of Halflings in the Vales of Anduin. The Lord of the Nazgûl decides to seek northward for
the Shire.Sept 18 Black Riders cross the Fords of Isen.Sept 20 Black Riders arrive at Isengard.Sept 22 Black Riders reach Sarn Ford and drive off the guard of Rangers.Sept 23 four Riders enter the Shire before dawn, the others pursue the Rangers eastward, then return to watch the Greenway. One rider comes to Hobbiton at nightfall.Sept 29Merry encounters at least one Black Rider in Bree in the evening.Sept 30 Early in the morning Black Riders break into the House at Crickhollow. According to A Knife in the Dark there were three, although at The Council of Elrond, Gandalf speaks of the four Black Riders who "invaded the Shire."
Close to the same time there is an attack on the Prancing Pony. It is suggested that the Black Riders did not personally attack the inn, but rather induced some of the men to do their work; the implication is that 'squint-eyed' southron, and Bill Ferny were of the group. During this time the Black Captain stays hidden south of Bree at Andrath.
That night at least five Riders throw down the gates at Bree and ride through the town.Oct 3 Gandalf attacked by nine Riders at night on Weathertop; when he escapes, four Riders follow him.Oct 6 Five Black Riders attack the hobbits and Strider at Weathertop.Oct 11Glorfindeldrives three Riders off the bridge of Mitheithel, while pursuing them he comes upon two others.Oct 20 Escape from the Riders at the Ford of Bruinen, the flood leaves the Riders uncloaked and unhorsed.

3019Feb 22Legolas shoots winged steed of a Nazgûl from the banks of the Anduin. March 5 One of the Nazgûl seen over camp of the Rohirrim.March 10 Five Nazgûl harry Faramir and his men. The Nazgûl retreat at the white flame from Gandalf's hand.March 11 Nazgûl seen high above the city of Minas Tirith.March 12 The forces of Sauron, led by the Lord of the Nazgûl, issue from the Minas Morgul and draw near to Osgiliath.March 13 Nazgûl again harry the retreat of Gondor's forces from Osgiliath. Faramir falls to the Black Breath.March 15 Witch-king breaks the Gate of Minas Tirith, withdrawing when the horns of Rohan blow. During the battle on Pelennor Fields he is killed by Éowyn aided by Merry.March 25 Nazgûl are present at the Battle of the Morannon. The Eagles attack them, but they are already retreating: Sauron summoned them when he perceived Frodo wearing the Ring.

Dates in this section come mostly from The Return of the King, LoTR Appendix B, The Tale of Years. The detailed movements of the Nazgûl from July through October of 3018 are augmented with material from Unfinished Tales, Part 3, Ch 4, The Hunt for the Ring.